Transducers using piezoelectric technologies are used for precise positioning at the nanometer scale. Typically, piezoelectric devices include a ceramic that is formed into a capacitor that changes shape when charged and discharged. These piezoelectric devices can be used as a position actuator because of this shape change property (i.e., vibrations). When the piezoelectric device is used as a position actuator, the shape change is approximately proportional to the applied voltage.
Ultrasonic drivers use these piezoelectric generated vibrations to create continuous movement with high speed, high torque, small size and quiet operation. An exemplary prior art ultrasonic driving system includes a cylinder that supports a threaded nut. The cylinder includes four symmetrically positioned piezoelectric transducers to simultaneous excite the orthogonal bending modes of the cylinder at the first bending mode resonant frequency in the ultrasonic range with a plus or minus 90-degree phase shift in a circular orbit. The threaded nut orbits a threaded shaft at the first bending mode resonant frequency, which generates torque that rotates the threaded shaft that moves the threaded shaft linearly.
Many ultrasonic drivers typically operate at speeds in the range of 100 mm/s to even 1000 mm/s. However, this speed is too fast for precise position control of image sensors and optical camera systems. The image sensors and the sensor's algorithm cannot capture images with sufficient quality because the motion is unstable and the step resolution is poor.